1. Field of the Invention
The invention relates to a device for mass transfer between fluids with interposition of a diaphragm unit consisting of two diaphragms and an intermediary diaphragm support, which diaphragm unit is pleated to a folded package and placed in a box-like enveloping case with inlets and outlets for the fluids, in such a manner that the pleats and the enclosed diaphragm support form several separate parallel flow paths, in which structure the pleats are open in the direction of distribution channels which are arranged rectangularly to the longitudinal pleat edges of the folding package in the case and serve as inlets and outlets for the fluids conveyed in the pleats.
2. Prior Art
Such a device is known e.g. for carrying out an ultrafiltration, from U.S. Pat. No. 3,965,012 and German Utility Model Pat. No. 1,477,779. Furthermore, a dialyzer for the treatment of blood with pleat structure is known (U.S. Pat. No. 3,864,265 and U.S. Pat. No. 4,028,252) wherein a diaphragm together with a diaphragm support are jointly pleated in the form of a grid system to a folding package. In this case, the two separate flow paths serve to convey the dialysate and the blood.
In filtration units for the treatment of blood, it is also basically known to use in flat diaphragms of hose-like or plate-like shape a fabric as the diaphragm support (U.S. Pat. No. 3,579,441 and German Offenlegungsschrift No. 2,653,875).
Furthermore, in dialyzers of coil structure or plate structure, it is known to use stamped foils of plastic material as the diaphragm support (German Offenlegungsschrift No. 2,747,904, corresponding to U.S. Application Ser. No. 742,359 now U.S. Pat. 4,115,273, Winstead; U.S. Pat. No. 3,738,813; U.S. Pat. No. 3,490,523; U.S. Pat. No. 3,362,540; and U.S. Pat. No. 3,960,730). The bilaterally arranged stampings form a multiplicity of punctiform or linear supports for the diaphragm and are furthermore arranged in a structure that favors the fluid flow of the fluids to be treated in the proper direction.
The invention relates also to a further development of the patent rights of the applicant according to U.S. Patent Application Ser. No. 6,384 now U.S. Pat. No. 4,219,422 and German Utility Model Patent Offenlegungsschrift No. 2,013,105.
Such pleat dialyzers are well suited for industrial manufacture since they are produced from endless material, namely of the diaphragm and the diaphragm support, by parallel pleating, and in this manner relatively small devices, i.e. filter elements, can be made.
Such filter elements should ideally absorb a relatively small blood volume, they should permit a uniform distribution of the blood flow over the diaphragm, they should offer the smallest possible resistance to flow on the blood side, present a high dialyzing efficiency, a good ultrafiltration rate, a compact structure, and their cost of manufacture should be low.
The latter fact is particularly important since these filter elements, after having been used once, are thrown away for safety reasons when they are, according to their purpose, employed as an artificial kidney.
The known filter elements manufactured according to the pleating principle need improvement insofar as the blood distribution from the side into the pleat depth and the further conveyance of the blood in the longitudinal direction, i.e. parallel to the pleats, is still too uneven and therefore no uniform blood film thickness over the entire area of the diaphragm can be achieved. Besides, in the case of employment of a simple fabric in binding cloth or of a non-interwoven network, the resistance to flow resulting therefrom is still too great.